The degradation behavior of hydrated lime sorbent exposed to a humid environment was investigated in terms of a change of the pore structure, phase transition, and particle aggregation. Di-ethylene glycol (DEG)-coated quicklime was hydrated to prepare a sorbent with a high surface area. The hydrated lime sorbent was maintained in a consistent chamber at 50 οC and 60% relative humidity for 168 h. As the degradation time of the sorbents exposed to the humid environment was increased, the calcite phase fraction was increased due to the carbonation process, whereas the reactivity for SO2 gas was reduced. A decrease in the specific surface area of the sorbents, from 45.8 m2/g to 7.6 m2/g, was also observed with elapsed degradation time. Also the clogging of small size pores having a size range of 30~40Å was observed due to the particle aggregation and the carbonation process by the humidity. Consequently, the degradation of hydrated lime sorbent in a humid environment was attributed to a collapse of the pore structure originating from the carbonation process and the particle aggregation.

Keywords: Hydrated lime sorbent, Humid environment, Pore structure, Particle aggregation, Carbonation process.